1. Field of the Invention
The present invention relates to an apparatus and method for inspecting the appearance of a semiconductor device having leads extending from its package, by inspecting the bending of each lead.
2. Description of the Related Art
A semiconductor device sealed by a package has leads extending from the side surfaces. These leads are trimmed and formed so that they are bent into a desired form to make gull wing leads, J leads, or other leads.
In order to examine whether the bending of each lead of the semiconductor device satisfies certain requirements, the appearance of the semiconductor device is normally inspected.
FIG. 1 is a schematic perspective view of an apparatus for inspecting the appearance of the semiconductor device, indicated by numeral 3. This semiconductor device 3 is equipped with a package 4 which has leads 5 extending from the sides. The appearance-inspecting apparatus, generally indicated by reference numeral 1, comprises an optical reading mechanism 2 consisting of a CCD image sensor, line sensor, or the like. The reading mechanism 2 is disposed at one side of the package 4 of the semiconductor device 3. An image of the leads 5 extending from the sides of the package 4 can be read by the optical reading mechanism 2.
The appearance of the semiconductor device 3 is inspected by the apparatus 1 in the manner now described. First, the optical reading mechanism 2 is placed at one side of the package 4 of the semiconductor device 3. An image of the leads 5 extending from the sides of the semiconductor device 3 is read by the optical reading mechanism 2. The bending of each lead 5 is calculated from the image of the side surface of the semiconductor device 3 read by the reading mechanism 2. Then, it is determined whether the calculated value is within a given range. In this way, the semiconductor device 3 is judged to be acceptable or not.
For example, where the package 4 consists of a quad flat package (QFP) and the leads 5 extend from the four sides of the package 4, an image of one side of the device is read. Then, the semiconductor device 3 is rotated through 90.degree. within the plane of the top surface of the device 3, followed by reading of the next side image. Reading of this kind is repeated. In this manner, images of the four sides are obtained.
The apparatus and method for inspecting the appearance of the semiconductor device constructed as described above have the following problems. The optical reading mechanism disposed at one side of the semiconductor device can obtain only one frame of image from each one side surface of the semiconductor device. Therefore, it is necessary to obtain plural frames of image according to the number of sides from which leads extend. This complicates the processing for judging whether the semiconductor device is acceptable or not. Also, the structure of the apparatus is rendered complex.
In the inspection method using this appearance-inspecting apparatus, it is necessary to rotate the semiconductor device according to the number of the sides from which leads extend and to obtain images of the individual sides. Furthermore, it is difficult to shorten the inspection time because each different image is judged separately.
Accordingly, placement of optical reading mechanisms on the sides of all the side surfaces from which leads extend may be contemplated. This makes it unnecessary to rotate the semiconductor device but the structure of the apparatus cannot be readily simplified.